In the manufacture of many electronic devices, for example printed circuit boards used in computers and other types of electronic devices, components are assembled onto a frame or printed circuit board (PCB) moving along an assembly line past a linear array of machines, each of which picks a given component from a supply of such components and places it in the proper location and orientation on the frame or board. Surface Mount Technology (SMT) for assembly of printed circuit and other boards typically uses this arrangement. Such machines are known in the art as “pick-and-place” machines or robots and may also be characterized as an end-effector. Typically, each pick-and-place machine is served by a dedicated feeder machine which unwinds a reel of tape containing the given components in sequence at a proper spacing and orientation, and presents each component sequentially for pickup and transfer by a vacuum head of the associated with the end-effector or pick-and-place machine. The components may be loosely attached to the tape by low-tack adhesive on the tape surface or may reside in shallow depressions in the tape, which depressions may be covered by a second, removable tape. Advance of the feeder tape drive is synchronized with the advance of the main assembly line and the cycle of the pick-and-place machine to present each component to the pick-and-place machine precisely where it is needed and when it is needed, and to do so with a high degree of positional and orientational accuracy. To meet these stringent requirements reliably, the feeder tape may be provided with perforations along one or both edges and may be driven by an intermittent sprocket advance mechanism. An example of such a tape feeder machine is the Model MPFO2, available from Hover-Davis, Inc., Spencerport, N.Y. USA.
Heretofore, the application of labels to surface mount and printed circuit assemblies was generally accomplished by a manual operation, whereby an operator placed the label on a printed circuit board. In some situations a robotic operation, at a station subsequent to the assembly operation, was used to place labels on the surface of the completed PCB assemblies. However, as will be appreciated, such additional steps are costly either in direct labor or as capital investments for automation.
Accordingly in SMT and similar applications, it is desirable to pick and place an adhesive-backed label onto a circuit board or other substrate in the same manner that is used for conventional SMT components. Moreover, it is a significant commercial advantage if the equipment to feed labels for pickup by conventional pick-and-place equipment is adaptable to operate in the same equipment and fashion as the component feeding devices currently used—thereby avoiding the need for modifications or additions to existing SMT assembly equipment. It should be appreciated that the adhesive or tacky force of a label to be used on a printed circuit board is significant as such labels are frequently required to remain affixed while the printed circuit board is exposed to extreme environments. For example, the board and attached label may pass through a wave soldering environment or a re-flow oven.
The discrete labels are commonly available in roll form, being peelably attached to a continuous ribbon or web of sacrificial backing material known generally as label liner. A conventional tape feeder machine is neither suited nor adaptable to providing peeled labels ready for picking because a) it is not capable of peeling such a label from a continuous backing liner, b) a peeled label in presentation position for acquisition by a pick-and-place machine will adhere unacceptably to the tape, and c) the label must be positioned in a close-tolerance, consistent manner in order to allow for accurate retrieval and placement by the pick and place machine in the same manner as components are retrieved and placed. Further, commonly available linered label stock is not perforated and thus cannot be advanced incrementally and reliably if simply substituted for the tape in a tape feeder machine.
Machines are known in the label printing art that can remove adhesive-backed labels from label liner stock and can present them sequentially for use. See, for example, U.S. Pat. No. 4,025,067 issued May 24, 1977 to Schlacht; U.S. Pat. No. 4,267,006 issued May 12, 1981 to Karn; U.S. Pat. No. 4,717,059 issued Jan. 5, 1988 to Takahashi et al.; U.S. Pat. No. 4,769,103 issued Sep. 6, 1988 to Koike et al.; and U.S. Pat. No. 5,642,666 issued Jul. 1, 1997 to Petteruti et al. Typically, such machines present a peeled label as partially adhered to, and partially projecting unsupported from, a ridged feeder lip to facilitate access to the adhesive side of the label for ready transfer or direct application to a substrate. Peeled labels may exhibit substantial curl, and thus the spatial location of such a label may not be precisely controlled. Known lips of linered label printers, therefore, are inherently inadequate to meet the high-tolerance label positioning requirements of an automatic pick-and-place machine.
Thus, there is a need for a feeder apparatus which can automatically convey a roll of linered label stock (or similar components), sequentially peel adhesive-backed labels from the liner, and present the labels sequentially with their adhesive sides toward a non-adherable platform for picking by attachment to their non-adhesive sides. The labels must be presented to the picker with a high degree of positional, orientational, and timing accuracy (i.e. close tolerances) and must be held substantially planar on the platform.
It is a principal object of the invention to provide a label feeding method and apparatus that can peel and present an adhesive-backed label for acquisition by a pick-and-place machine or robot in a conventional surface mount assembly system. It is a further object of the invention to provide a label feeder that can present an adhesive-backed label with a high degree of positional, orientational, and timing accuracy. It is yet another object of the invention to provide a platform for adhesive-backed materials to which such materials may not substantially adhere, from which such materials are easily lifted, and upon which such materials are maintained in a substantially planar form.
Briefly described, a label feeder embodying the invention has a web path including apparatus for mounting, unwinding, and conveying a roll of liner stock bearing a sequential plurality of removably adhered labels on a surface thereof. The label liner is pulled through the feeder by a driven take-up which preferably includes a capstan drive having opposed nip rollers, preferably axially fluted and meshed, driven by a motor, preferably a stepper motor. Advance of the stepper motor is controlled by a programmable electronic controller to advance the liner. The linered labels are led through a tensioner and around an acute-angle peeler edge that separates the labels from the liner in known fashion, the label stock having sufficient beam strength, and the adhesive having insufficient tack (adhesive force) to maintain adherence to the liner through such an abrupt turn in the web path. The peeling action advances the label onto and along a platform preferably comprising a bed of rollers formed of, or coated with, an inherently low-adherence material such as a fluoropolymer. When peeling of a label is completed, the label has been advanced onto the roller bed to precisely the proper location for acquisition by a pick-and-place machine. The proper location of a peeled label on the platform is confirmed by a sensor that signals the controller to stop the liner advance. The signal also serves to reset the apparatus for advance of the next label after the present label is picked from the roller bed.
In accordance with the present invention, there is provided a surface mount assembly system, including: means for presenting a substrate to be populated with one or more components on a surface thereof; a plurality of component feeders operatively associated with the surface mount assembly system, for presenting components at respective component pick-up locations; a robot for retrieving the components from said component feeders at the respective pick-up locations and placing the components on the surface of the printed circuit board; wherein at least one of said component feeders is a label feeder for feeding an adhesive-backed label on a label liner to the respective pick-up location for retrieval by the robot, and where said label feeder comprises a frame, a separator presenting an edge underlying the label liner for separating the label from the label liner; and a roller platform including a plurality of rollers disposed on said frame and facing the adhesive backing side of the label for receiving and supporting the adhesive side thereof, wherein at least two of said plurality of rollers include a plurality of circumferential ridges for supporting the label while reducing the adhesion of the label to the rollers.
In accordance with another aspect of the present invention, there is provided a label feeder for transporting an adhesive-backed label on a label liner, separating the label from the label liner, and presenting the separated label for retrieval, comprising: a frame; a separator disposed on said frame and presenting an edge underlying the label liner for separating the label from a label liner with the label adhesive backing side facing toward the liner; and a roller platform including a plurality of rollers disposed on said frame and facing the adhesive backing side of the label for receiving and supporting said separated label on the adhesive surface thereof, wherein at least two of said plurality of rollers include a plurality of circumferential ridges for supporting the label.
In accordance with another aspect of the present invention, there is provided a label feeder for separating an adhesive-backed label from a label liner and presenting the peeled label for acquisition by a pick-and-place machine, comprising: a frame; a peeler edge disposed on said frame for peeling a label from a label liner; a roller platform comprising a plurality of rollers disposed on said frame for receiving, conveying, and supporting said peeled label, at least one of said rollers being undercut over a portion of its surface to provide a plurality of circumferential ridges having a diameter greater than the diameter of said undercut portion, at least one of said rollers being substantially non-adherable to said adhesive-backed label over at least a portion of said circumferential ridges contactable with said adhesive; a web path along said frame passing around said peeler edge and past said platform along which said label liner is movable; a tensioner in said web path ahead of said peeler edge; drive means for pulling said label liner along said web path around said peeler edge, said drive means including a pair of nip rollers disposed respectively one on either side of said web path to engage said label liner therebetween, at least one of said nip rollers being driven; a sensor for sensing the presence and absence of a peeled label on said platform; and a programmable controller responsive to signals from said sensor for controlling operation of operating elements of said feeder.
In accordance with yet another aspect of the present invention, there is provided a method for providing a peeled, adhesive-backed label from a roll of linered label stock using a path for conveyance of the stock, comprising the steps of: advancing the label stock along said web path using label stock drive means; separating the label from the label liner using a separating edge underlying the label liner; receiving the label on a platform including a plurality of ridged rollers, wherein the adhesive-backed surface of the label contacts the ridges of the rollers; using a sensor, sensing the presence and absence of a separated label on said platform and communicating said presence and absence to said drive means; in response to a label absence signal from said sensor, energizing said drive means to advance the label stock around said separating means to separate a label from said stock; and in response to a label presence signal from said sensor, de-energizing said drive means to arrest further advance of the label stock.
One aspect of the invention deals with a basic problem in the application of labels to printed circuit boards and similar electronic assemblies. Such systems generally employ standardized equipment that interface with pick-and-place robotic machines for the placement of electrical components (e.g., integrated circuits). Traditionally, labels were added or applied either manually or using dedicated labeling systems. An aspect of the present invention is further based on the discovery of a technique that enables the creation of a label feeding apparatus in a form factor compatible with conventional pick-and-place machines, for example, the Fuji IP/QP2 and the Universal GSM. The technique utilizes a linered label stock and a unique label feeder design and positioning platform to present the label in a manner consistent with the presentation of other components to be placed on a surface of the printed circuit board.
The technique described above is advantageous because it efficiently enables the use of a label feeder that may be interchanged with other component-type feeders in a pick-and-place system. The techniques make it unnecessary to have manual label application or a dedicated label-feeding station. As a result of the invention, it is possible to integrate label-feeding technology into component placement equipment.
The present invention will be described in connection with a preferred embodiment, however, it will be understood that there is no intent to limit the invention to the embodiment described. On the contrary, the intent is to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.